1. Field of the Invention
The present invention relates to a liquid crystal display, and more particularly, to a liquid crystal display (LCD) bonding apparatus and method for fabrication of large-sized LCDs using a liquid crystal dropping method applied thereto.
2. Background of the Related Art
In general, as demands for various types of display devices increases, different flat display panels, such as liquid crystal display (LCD), plasma display panel (PDP), electro-luminescent display (ELD), and vacuum fluorescent display (VFD) devices are currently being developed for deployment as display device in various apparatus. Of these different flat display panel devices, the LCDs have been commonly used as portable display devices, and are replacing the cathode ray tube (CRT) because of their excellent picture quality, light weight, thin profile, and low power consumption. In addition, the mobile type LCDs, such as monitors for notebook computers, are presently being developed for televisions and monitors of computers.
Despite various technical developments of the LCD devices, enhancement of picture quality are inconsistent with the features and advantages of the LCD. Accordingly, key development of the LCD device relies on implementation of high picture quality (i.e., high definition), high luminance, and large-sized screen while maintaining its light weight, thin profile, and low power consumption.
The LCD device is commonly provided with a liquid crystal panel for displaying an image, and a driving part for providing a driving signal to the liquid crystal panel. The liquid crystal panel includes a TFT array substrate and a color filter substrate that are bonded together with a gap between the substrates, and a liquid crystal material layer injected within the gap.
On the TFT array substrate, there are a plurality of gate lines arranged along a first direction at fixed intervals, a plurality of data lines arranged along a second direction at fixed intervals perpendicular to the gate lines, a plurality of pixel electrodes disposed in pixel regions defined at crossed points of the gate and data lines to form a matrix, a plurality of thin film transistors switchable in response to a signal applied to the gate lines for transmission of a signal transmitted along the data line to the pixel electrodes.
On the color filter substrate, there is a black matrix layer for shielding light from portions of the color filter substrate excluding the pixel regions, a red (R), green (G), and blue (B) color filter layer for converting white light into colored light, and a common electrode for generating an applied electric field.
The LCD device may be fabricated by a known liquid crystal injection method in which sealant is patterned on one of the TFT and color filter substrates with an injection hole formed thereon, bonding the substrates under a reduced pressure (i.e., a vacuum), and injecting the liquid crystal material through the injection hole in the sealant. Alternatively, LCD devices may be fabricated by a known liquid crystal dropping method, as disclosed in a Japanese laid-open patent publication Nos. H11-089612, and H11-172903. In the liquid crystal dropping method, a first substrate having the liquid crystal material dropped thereon and a second substrate are bonded together in a vacuum chamber. However, the LCD device fabricating method having the liquid crystal injection method applied thereto requires a substantial amount of processing time period for injection of the liquid crystal material. For example, since the liquid crystal material is injected through capillary action under a vacuum, the liquid crystal material injection is not favorable for fabrication of large-sized LCD devices and for mass production. In contrast, the liquid crystal fabricating method using the liquid crystal dropping method does not require injection processing, thereby reducing a total amount of processing time.
FIG. 1 is a cross sectional view of a liquid crystal display device bonding apparatus during loading according to the related art. In FIG. 1, the liquid crystal display device bonding apparatus includes a frame 10, an upper stage 21, a lower stage 22, a sealant dispenser (not shown), a liquid crystal dispenser 30, an upper chamber part 31, a lower chamber part 32, chamber moving system 40, a capture system 61-64, and a stage moving system 50.
The lower stage 22, sealant dispenser (not shown), and liquid crystal dispenser 30 are disposed along a side of the frame, and the upper and lower chamber parts 31 and 32 are separated. Accordingly, once a lower substrate 51 has been placed onto the lower stage 22 and the liquid crystal material and sealant are deposited onto the lower substrate 51, the lower chamber part 32 is moved beneath the upper chamber part 31 via the stage moving system 40 prior to bonding.
FIG. 2 is a cross sectional view of the liquid crystal display device bonding apparatus of FIG. 1 during bonding according to the related art. In FIG. 2, the lower chamber part 32 is positioned beneath the upper chamber part 31, and the upper and lower chamber parts 31 and 32 are connected together. The capture system includes the rotating shaft 61, the rotating actuator 63, the elevating actuator 64, and the supporting plate 62 for supporting a corner of the substrate. The capture system supports an upper substrate 52 to be temporarily held to the upper stage 21 at opposite diagonal positions thereof.
A method for fabricating an LCD device by using the substrate apparatus according to the related art will be explained in more detail during a fabrication process.
The upper substrate 52 is held at the upper stage 21, and the lower substrate 51 is held at the lower stage 22. Accordingly, the lower chamber part 32 having the lower stage 22 is moved to a location for processing a sealant coating and liquid crystal dropping by the chamber moving system 40 as shown in FIG. 1. Then, upon finishing the sealant coating and liquid crystal dropping onto the lower substrate 51 by the sealant dispenser (not shown) and liquid crystal dispenser 30, the lower chamber part 32 is moved beneath the upper chamber part 31 by the chamber moving system 40, as shown in FIG. 2. Next, assembly of the upper and lower chamber parts 31 and 32 is performed by the chamber moving system 40 to enclose a space where the upper and lower stages 21 and 22 are located. Then, the supporting plate 62 is brought to two corners of the upper substrate 52 held at the upper stage 31 as the elevating actuator 64 and the rotating actuator 63 of the capture system move.
FIG. 3 is a perspective view of a substrate supporting system of a liquid crystal display device bonding apparatus according to the related art. In FIG. 3, a suction force generated by a vacuum system (not shown) that holds the upper substrate 52 is released, thereby dropping the upper substrate 52 onto the supporting plates 62 of the capture system. In addition, the vacuum system (not shown) is used for reducing a pressure within the assembled upper and lower chamber parts 31 and 32. When the assembled upper and lower chamber parts 31 and 32 have achieved a desired vacuum, an electrostatic force is applied to the upper stage 31, thereby affixing the upper substrate 52 to the upper stage 21. Then, the rotating actuator 63 and the elevating actuator 64 of the capture system are driven, thereby moving the supporting plates 62 and the rotating shaft 61 out of the way.
During the period of the desired vacuum, the upper stage 21 is moved downward by the stage moving means 50 to press and bond the upper substrate 52 held at the upper stage 21 to the lower substrate 51 held at the lower stage 22, thereby completing fabrication of the LCD device.
During the fabrication process, as detailed above, many of the moving elements in the chamber part require substantial moving accuracy (i.e., the stages and the substrate supporting system) and also require substantial accurate position setting. The position setting of the moving elements is generally made during initial equipment installation, or after a predetermined operational time period. Accordingly, repeated manual position setting of the moving elements results in poor accuracy and requires significantly long periods of time. Moreover, the position setting of the moving elements cannot anticipate sudden occurrences of unexpected situations, such as power loss. For example, the controller of the bonding apparatus may only remember positions of respective moving elements as original positions at the moment power is restored, thereby resulting in inaccurate positioning of the moving elements.